1. Field of the Invention
This invention is related to systems employing electronic digital computers for determining the torque applied by a power producing device to a torque converter and other components of an automotive drivetrain. More particularly, the present invention is related to the field of digital circuits that process information indicative of the instantaneous operating characteristics of the drivetrain and adapt it for use by a computer in determining the various torques. More particularly still, the invention pertains to such digitial circuits wherein transient operation of an automatic transmission, excessive disparity in the speeds of several shafts of the drivetrain and other operating conditions are sensed, transmitted to the computer and used to confirm the acceptability of data or to discount the data produced by the circuits in the computations made by the computer.
2. Description of the Prior Art
In the operation of an automatic transmission, the determination of the shift points and control of the line pressure that actuates the clutch elements in the planetary gear set require that the operating characteristics of the engine and of the transmission be accurately known. Control systems for automatic transmissions that are based on hydraulic fluid logic or electronically controlled logic employ various indirect indications of the instantaneous operating characteristics of the engine and of the transmission. These indications with reference to U.S. patents in which they are described include: vehicle speed and accelerator pedal displacement (U.S. Pat. Nos. 3,732,754 and 4,034,627); throttle valve setting (U.S. Pat. Nos. 3,733,930 and 4,082,013); transmission output shaft torque (U.S. Pat. Nos. 4,031,782 and 4,106,368); output shaft speed (U.S. Pat. No. 4,027,554); sungear acceleration (U.S. Pat. No. 3,719,096); turbine torque, turbine acceleration and instantaneous gear ratio (U.S. Pat. No. 3,752,011); slip rate of the torque converter (U.S. Pat. No. 3,640,152); manifold pressure and torque converter slippage (U.S. Pat. No. 3,693,479); and output torque of the engine in combination with the torque on the stator of the torque converter (U.S. Pat. No. 3,799,001). Fluid circuit logic used to control operation of an automatic transmission employs pressure levels as a measure of the rotational speed of critical components of the transmission. For example, governor pump pressure is used as a measure of the speed of the output shaft of the transmission. Precise knowledge of the torque at various locations in the drivetrain is essential for optimum control of the transmission.
For example, it is preferable to know exactly the torque produced by the engine throughout the full range of its operation. In an automatic transmission the engine drives the planetary gear sets through a torque converter whose impeller is driven from the engine and whose turbine drives the transmission, the impeller and turbine being driveably connected through a hydrodynamic flow path. Because of the packaging limitations required in an automotive vehicle, it is difficult to determine with accuracy the power or torque delivered by the engine although the speed of the engine crankshaft can be readily deduced.
The operating characteristics of a hydrodynamic torque converter are fairly well established. For example, the relationship between the torque of the turbine and the impeller torque is a well established function of the speed ratio of the shafts on which each of these are mounted. Similarly, the torque converter capacity factor defined as the ratio of the speed of the impeller to the square root of the torque of the impeller is known to vary in accordance with well established principles according to variations of the speed ratio of the torque converter. The rotational speeds of the several shafts that connect the driveshafts of the vehicle with the engine crankshaft are generally easily determined by using information concerning operation of the torque converter. Shaft speed can be used to accurately determine torque delivered from the engine and torque at various locations along the drivetrain.